Antifungal polypeptides, e.g. lectins, have been isolated from monocotyledonous and dicotyledonous plants [Ramshaw, J. A. M. (1982) in Nucleic Acids and Proteins in Plants I. Encyclopedia of Plant Physiology, New Series, (Boulter, D. and Parthier, B. editors.) vol. 14 A, pp. 229-279, Springer, Berlin]. It has also been observed that the biosynthesis of thionine is initiated by infestation of the plant with pathogenic fungi. It is therefore assumed that this protein possesses antifungal activity [Bohlmann, H. et al. (1989) EMBO J. 7, 1559-1565; Broekaert, W. F. et al. (1989) Science 245, 1100-1102].
Antifungal polypeptides have also been isolated from microorganisms. For example, a similar protein has been detected in the fermentation broth of Aspergillus giganteus (Olson, B. M. & Goerner, G. L. (1965) Appl. Microbiol. 13, 314-321), but the amino acid sequence of said protein is two lysine residues shorter than that of the protein according to the invention.
We have now been able to isolate a polypeptide with antifungal action from Aspergillus giganteus and determine its sequence.
The nucleotide sequence of the peptide claimed has been published by Wnendt et al. (Nucl. Acids Res. 18, p. 3987, September 1990).
We have moreover found that expression, in plants, of the gene which codes for the polypeptide claimed in the main patent application cited above strongly inhibits the growth of phytopathogenic fungi on the plant.